From 8e48dcfbd7c0892b4cfd064d682cc4c95a29df32 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Sun, 16 May 2010 18:00:00 -0400 Subject: [PATCH] ext4: Use our own write_cache_pages() Make a copy of write_cache_pages() for the benefit of ext4_da_writepages(). This allows us to simplify the code some, and will allow us to further customize the code in future patches. There are some nasty hacks in write_cache_pages(), which Linus has (correctly) characterized as vile. I've just copied it into write_cache_pages_da(), without trying to clean those bits up lest I break something in the ext4's delalloc implementation, which is a bit fragile right now. This will allow Dave Chinner to clean up write_cache_pages() in mm/page-writeback.c, without worrying about breaking ext4. Eventually write_cache_pages_da() will go away when I rewrite ext4's delayed allocation and create a general ext4_writepages() which is used for all of ext4's writeback. Until now this is the lowest risk way to clean up the core write_cache_pages() function. Signed-off-by: "Theodore Ts'o" Cc: Dave Chinner --- fs/ext4/inode.c | 141 ++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 119 insertions(+), 22 deletions(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 6aa0442811d2..830336d3911b 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2426,17 +2426,6 @@ static int __mpage_da_writepage(struct page *page, struct buffer_head *bh, *head; sector_t logical; - if (mpd->io_done) { - /* - * Rest of the page in the page_vec - * redirty then and skip then. We will - * try to write them again after - * starting a new transaction - */ - redirty_page_for_writepage(wbc, page); - unlock_page(page); - return MPAGE_DA_EXTENT_TAIL; - } /* * Can we merge this page to current extent? */ @@ -2831,6 +2820,124 @@ static int ext4_da_writepages_trans_blocks(struct inode *inode) return ext4_chunk_trans_blocks(inode, max_blocks); } +/* + * write_cache_pages_da - walk the list of dirty pages of the given + * address space and call the callback function (which usually writes + * the pages). + * + * This is a forked version of write_cache_pages(). Differences: + * Range cyclic is ignored. + * no_nrwrite_index_update is always presumed true + */ +static int write_cache_pages_da(struct address_space *mapping, + struct writeback_control *wbc, + struct mpage_da_data *mpd) +{ + int ret = 0; + int done = 0; + struct pagevec pvec; + int nr_pages; + pgoff_t index; + pgoff_t end; /* Inclusive */ + long nr_to_write = wbc->nr_to_write; + + pagevec_init(&pvec, 0); + index = wbc->range_start >> PAGE_CACHE_SHIFT; + end = wbc->range_end >> PAGE_CACHE_SHIFT; + + while (!done && (index <= end)) { + int i; + + nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, + PAGECACHE_TAG_DIRTY, + min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1); + if (nr_pages == 0) + break; + + for (i = 0; i < nr_pages; i++) { + struct page *page = pvec.pages[i]; + + /* + * At this point, the page may be truncated or + * invalidated (changing page->mapping to NULL), or + * even swizzled back from swapper_space to tmpfs file + * mapping. However, page->index will not change + * because we have a reference on the page. + */ + if (page->index > end) { + done = 1; + break; + } + + lock_page(page); + + /* + * Page truncated or invalidated. We can freely skip it + * then, even for data integrity operations: the page + * has disappeared concurrently, so there could be no + * real expectation of this data interity operation + * even if there is now a new, dirty page at the same + * pagecache address. + */ + if (unlikely(page->mapping != mapping)) { +continue_unlock: + unlock_page(page); + continue; + } + + if (!PageDirty(page)) { + /* someone wrote it for us */ + goto continue_unlock; + } + + if (PageWriteback(page)) { + if (wbc->sync_mode != WB_SYNC_NONE) + wait_on_page_writeback(page); + else + goto continue_unlock; + } + + BUG_ON(PageWriteback(page)); + if (!clear_page_dirty_for_io(page)) + goto continue_unlock; + + ret = __mpage_da_writepage(page, wbc, mpd); + if (unlikely(ret)) { + if (ret == AOP_WRITEPAGE_ACTIVATE) { + unlock_page(page); + ret = 0; + } else { + done = 1; + break; + } + } + + if (nr_to_write > 0) { + nr_to_write--; + if (nr_to_write == 0 && + wbc->sync_mode == WB_SYNC_NONE) { + /* + * We stop writing back only if we are + * not doing integrity sync. In case of + * integrity sync we have to keep going + * because someone may be concurrently + * dirtying pages, and we might have + * synced a lot of newly appeared dirty + * pages, but have not synced all of the + * old dirty pages. + */ + done = 1; + break; + } + } + } + pagevec_release(&pvec); + cond_resched(); + } + return ret; +} + + static int ext4_da_writepages(struct address_space *mapping, struct writeback_control *wbc) { @@ -2839,7 +2946,6 @@ static int ext4_da_writepages(struct address_space *mapping, handle_t *handle = NULL; struct mpage_da_data mpd; struct inode *inode = mapping->host; - int no_nrwrite_index_update; int pages_written = 0; long pages_skipped; unsigned int max_pages; @@ -2919,12 +3025,6 @@ static int ext4_da_writepages(struct address_space *mapping, mpd.wbc = wbc; mpd.inode = mapping->host; - /* - * we don't want write_cache_pages to update - * nr_to_write and writeback_index - */ - no_nrwrite_index_update = wbc->no_nrwrite_index_update; - wbc->no_nrwrite_index_update = 1; pages_skipped = wbc->pages_skipped; retry: @@ -2966,8 +3066,7 @@ retry: mpd.io_done = 0; mpd.pages_written = 0; mpd.retval = 0; - ret = write_cache_pages(mapping, wbc, __mpage_da_writepage, - &mpd); + ret = write_cache_pages_da(mapping, wbc, &mpd); /* * If we have a contiguous extent of pages and we * haven't done the I/O yet, map the blocks and submit @@ -3033,8 +3132,6 @@ retry: mapping->writeback_index = index; out_writepages: - if (!no_nrwrite_index_update) - wbc->no_nrwrite_index_update = 0; wbc->nr_to_write -= nr_to_writebump; wbc->range_start = range_start; trace_ext4_da_writepages_result(inode, wbc, ret, pages_written); -- 2.20.1